Electrochemical and optical properties of solution processable benzotriazole and benzothiadiazole containing copolymers

2-Dodecyl benzotriazole (BTz) and benzothiadiazole (BTd) containing alternating copolymers poly(4-(2-dodecyl-2H-benzo[d][1,2,3]triazol-4-yl)benzo[c][1,2,5]thiadiazole (P1), poly(4-(5-(2-dodecyl-7-(thiophen-2yl)-2H-benzo[d][1,2,3]triazol-4-yl)thiophen-2-yl)benzo[c] [1,2,5] thiadiazole (P2) and poly(4-(5-(2-dodecyl-7-(4-hexylthiophen-2-yl)-2H-benzo[d] [1,2,3]triazol-4-yl) -3-hexylthiophen-2-yl) benzo[c][1,2,5] thiadiazole (P3) were synthesized via Suzuki polycondensation reactions. The solubility of the polymers enabled spray coating to carry out the electrochemical and optical studies. Electronic and optical properties of resulting polymers showed that P2 is a great candidate to be used as processable blue electrochromic polymer which can switch to transparent upon oxidation. P3 was also investigated in terms of its electrochromic performance which has two different colored and a transparent states, whereas P1 does not exhibit any spectral change upon applied potentials. HOMO and LUMO values, band gaps and kinetic behavior of polymers upon externally applied potential are reported in detail.

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► Polymers contain benzotriazole and benzothiadiazole acceptors on their backbones.
► This study shows that polymers would be great candidates for optoelectronic devices.
► Polymers have ambipolar characteristic and moderate band gaps.